1. Field of the Invention
This invention relates to a rewritable recording/display apparatus using a rewritable recording film capable of repeatingly recording or erasing information and to a method of erasing a record.
2. Description of the Related Art
Apparatuses such as thermal recording apparatuses or thermal transfer recording apparatuses in which a heating means, e.g., a thermal head or laser light is used to perform recording or display are applied to various kinds of recording/display apparatuses including printers, facsimile apparatuses and displays. For example, for a recording unit of a facsimile apparatus using a thermal recording sheet, a method is ordinarily used in which an image is formed based on selectively energizing heating elements on a thermal head at predetermined times in accordance with an input recording signal so as to develop a color on the thermal recording sheet at desired positions. With respect to recording units of computers or word processors, thermal transfer type recording apparatuses are widely used in which heating elements of a thermal head are selectively energized to melt ink of an ink ribbon, the melted ink being transferred to a recording sheet. In the case of such thermal recording or thermal transfer recording, however, the recorded image cannot be erased and the same recording sheet cannot be used again to record a different desired image.
Examples of the conventional display and facsimile apparatuses will be described below.
FIG. 36 is a longitudinal sectional side view of a conventional display apparatus such as the one described in "Information display apparatus using a toner image" (Yojiro Ando et al , pp 119 to 122) of the theses of the workshop, Fine Image (Nihon Shashin Gakkai, Denshi Shashin Gakkai, SPSE Tokyo Branch, 1989).
As shown in FIG. 36, a frame 1 provided as a main body of the display apparatus has a front glass 2 which constitutes a display screen. Upper and lower sheet rollers 3 and 4 are disposed in the frame 1. A recording medium or recording sheet 5 is wrapped around and supported on the sheet rollers 3 and 4 and is moved therearound. The recording sheet 5 is formed of an endless belt on which a toner image is formed and displayed. A magnet roller 7 provided to form a toner image on the recording sheet 5 is controlled by a controller 8. A recording section for forming a toner image on the recording sheet includes toner 6, the magnet roller 7 and the controller 8. A driver IC 9 and a cleaner 10 for scraping off the toner image formed on the recording sheet 5 are also provided.
The operation of this apparatus is as described below. On the recording sheet 5 supported and fed by the upper and lower sheet rollers 3 and 4, a toner image is formed by the magnet roller 7 under the operation of the controller 8 during feeding of the recording sheet 5. After one frame of toner image has been formed, the recording sheet 5 is stopped to display the image. After being displayed, the toner image on the recording sheet 5 is scraped off by the cleaner 10 as the recording sheet 5 is moved. The recording sheet 5 and the toner thereby become ready for being used again.
FIG. 37 is a schematic longitudinal sectional side view of a conventional facsimile apparatus such as the one described on page 47(725) of Mitsubishi Denki Giho Vol.55, No.10, 1981. Energization pulses in accordance with a recording pattern to be recorded on a thermal recording sheet 13 described below are applied to a thermal head 11 to develop a colored image on the thermal recording sheet 13. An unrolled portion of a roll of thermal recording sheet 13 is led to the thermal head 11 along a transport guide 16a and is pressed against the thermal head 11 by a platen roller 14. The portion of thermal recording sheet 13 on which a colored image is recorded is guided to a discharge tray 1a by a transport guide 16b and guide rollers 15a and 15b.
The operation of this apparatus is as described below. Thermal recording sheet 13 is transported to the recording position between the thermal head 11 and the platen roller 14 by being led along the transport guide 16a. Energization pulses in accordance with a recording pattern to be recorded on the thermal recording sheet 13 are applied to the thermal head 11, and the thermal head 11 thereby produces heat to form a corresponding colored image on the thermal recording sheet by color development. The portion of thermal recording sheet 13 on which the colored image is formed is sent to the discharge tray la by being led by the guide rollers 15a, the transport guide 16b and the guide rollers 15b.
In the conventional display apparatus arranged as described above, the construction of the recording section including toner 6, magnet roller 7 and controller 8 is complicated. There are therefore the problems of difficulty in reducing the size of the recording section, impossibility of completely recovering and using toner 6, and need to resupply toner 6 and to perform maintenance operations. In the facsimile apparatus constructed as described above, thermal recording sheet 13 once used for recording cannot be used again, and new recording sheet 13 is required for each recording. The running cost of this apparatus is therefore high.
FIG. 38 is a cross-sectional view of a conventional facsimile apparatus such as the one described on page 210 of Nikkei Electronics, Nov. 16, 1987. A control unit (not shown) and other units are provided on a control circuit board 22. An original 26 is transported by a sheet feed roller 24. If a plurality of original sheets 26 are set, they are separated one by one by a separation member 25. The image on each original 26 is read by a close-contact type image sensor 27. The original 26 is brought into close contact with the image sensor 27 by a platen roller 28. The image read by the close-contact type image sensor 27 is recorded on a recording sheet 29 by a thermal head 30. The recording sheet 29 is brought into close contact with the thermal head 30 by a platen roller 31. The apparatus has a power source 21.
The operation of this apparatus is as described below. At the time of reception, an image signal received from a facsimile apparatus on the other end of the line is first supplied to the control circuit board 22. A decoding unit provided on the control circuit board 22 decodes the image signal into an image line by line and sends a recording signal corresponding to the image to the thermal head 30. Recording is effected on the recording sheet 29 based on the recording signal by the thermal head 30. The platen roller 31 is rotated to an extent corresponding to one line at a time to move the recording sheet 29 in a direction a. This operation is conducted with respect to one page to record the image corresponding to one page on the recording sheet 29. Needless to say, recording cannot be performed when the amount of remaining recording sheet 29 is zero. Ordinarily, the apparatus is unable to receive recording signals in such a case.
A type of facsimile apparatus is known in which a memory for storing image signals is provided on the control circuit board 22. This facsimile apparatus automatically stores received image signals in the memory when the amount of remaining recording sheet 29 is reduced to zero during reception. When recording sheet 29 is resupplied to enable the recording operation, the image corresponding to the image signals stored in the memory is recorded on the recording sheet automatically or by a recording instruction input through an operation panel 23. In a case where reception is started while there is no recording sheet 29, received image signals are stored in the memory.
At the time of transmission, original 26 is inserted to the position of the feed roller 24. The original 26 is moved in the direction b to the position of the close-contact type image sensor 27 by following the rotation of the feed roller 24. At this time, if a plurality of original sheets 26 are inserted in a superposed state, they are separated one by one by the separation member 25. The original 26 is moved by the platen roller 28 while the image is being read by the close-contact type image sensor 27. The image read by the image sensor 27 is encoded by an encoding unit provided on the control circuit board 22 and the encoded signal is transmitted to the terminal at the other end of the line designated through the operation panel 23.
The conventional facsimile apparatuses arranged as described above entail the following drawbacks. In the case of those having no memory, if the frequency of reception is high, recording sheets must be resupplied frequently, which is inconvenient for the user. Also the running cost is thereby increased.
Even if a memory is provided, troublesome user operations are also required. That is, a memory overflow easily occurs if the frequency of reception is high. In such a case, the reception cannot be continued and it is necessary to request that the original should be transmitted again from the other end.
In the case of recording/display apparatuses for word processors or computers, a document or a program is written by being frequently modified or corrected to be completed based on document data output to recording sheets or a program list (test printing is frequently effected). Recording sheets are thereby wasted and the writing cost per unit document or program is increased.
In a case where a document formed by a word processor or the like is corrected and checked while being displayed on the screen of a CRT or a liquid crystal display without being printed, the image of the document is ordinarily displayed by being reduced so that the whole of the document can be displayed in one frame. However, since the resolution of such display devices is ordinarily low, characters of the document cannot be formed finely and it is difficult to discriminate the characters to elaborate the sentences while continuously displaying the one-frame image. For this reason, the number of test prints and, hence, the running cost cannot be reduced.
Other apparatuses, such as those disclosed in Japanese Patent Laid-Open Nos.57-117978, 62-116191, 64-18353, 648354, and 64-18355, are also included in the related art.
On the other hand, rewritable recording films capable of repeated recording and erasing with a heating means such as a thermal head or laser light have recently been developed. For example, resin or organic low molecular weight materials films disclosed in U.S. Pat. No. 4,695,528, Japanese Patent Laid-Open Nos.55-154198 and 57-82086 and dyestuff films such as those disclosed in WO 90/11898 and Japanese Patent Laid-Open 02-188294 are known as such rewritable recording films.
More specifically, the former type is formed of a matrix material consisting of a thermoplastic resin or the like, and an organic low molecular weight material dispersed in the matrix material, and has characteristics such that its state is changed according to the temperature at which it is maintained, and which is higher than a particular temperature T0. That is, there are two state transition temperatures T1 and T2 (T1&lt;T2) higher than T0. When the film is cooled to a temperature equal to or lower than T0 after being heated and maintained at a temperature equal to or higher than T2, it becomes cloudy and is set in a maximum light shielding state. When the cloudy recording layer is cooled to a temperature equal to or lower than T0 after being heated and maintained at a temperature equal to or higher than T1 and lower than T2, it becomes transparent. These changes in state are mainly based on changes of the organic low molecular weight material in the recording layer.
The state of the latter type of rewritable recording film can be changed by energy control alone. That is, lactone rings are opened by high-temperature heating to form a compound having a color, and the lactone rings are closed by low-temperature heating to restore a colorless leuco compound. This phenomenon is due to the structure of the color developing/reducing agent and the reversibility of the leuco compound. As color developing/reducing agents, salt of gallic acid and aliphatic amine and other compounds are known. In the above-described examples, recording is effected by first thermal energy (high temperature) and erasing is effected by second thermal energy (low temperature), so that recording can be repeated only by controlling the thermal energy.
However, the above-described conventional recording and display apparatuses are not designed to use these rewritable recording films, and have no erasing function.